It is important in various industries for a customer receiving a shipment of goods on a railroad car or a trailer to expect the shipper to mechanically lock the door of the car or trailer by a tamper proof device to provide evidence to the customer that the contents of the car or trailer have not been changed since the time they were dispatched by the shipper. Similar devices are used at a part separation line in gas meters, electric meters, etc. to make sure there has been no tampering by vandals or the like.
The most well known seal device for this purpose involves a pre-formed lead seal having one end of a flexible cable secured therein. The free end of the cable projects through aligned holes in the handle, door or frame of the railroad car or trailer or between two separable housing parts of the meter. The free end of the cable then passes through an opening in the lead seal and the lead seal is deformed to frictionally lock the two ends of the cable therein. In order to move the two relatively movable pieces of the apparatus to be sealed, a person is required to sever the cable or disengage one end of the cable from the deformed lead seal. Thereby, any person observing the severed locking device is alerted to a prior opening.
U.S. Pat. No. 2,809,065 discloses two plastic parts having unique wedge-shaped configurations and a strip intermediate the two having flanged, serrated and wedge-shaped surfaces to lock the strip to the two plastic parts forming the seal. The strip passes through holes in apparatus to be secured. After the strip is secured to the two plastic parts and they are secured together, the strip must be severed or the plastic parts destroyed to open the secured apparatus.
U.S. Pat. No. 3,770,307 discloses a cable lock and seal device which comprises a flexible cable and an enclosure fixedly secured to one end of the cable. A passage extends through the enclosure and is proportioned slidably to receive the distal end portion of the cable therethrough. A wedge element and a disk-shaped jam element are sealed within the enclosure, the wedge element including a ramp surface disposed at a small angle with respect to the passage and laterally spaced apart therefrom. The jam element is frictionally engaged between the ramp surface and cable portion whereby, movement of the cable through the passage in one direction causes movement of the jam element laterally away therefrom and movement of the cable in a direction opposite the aforementioned direction causes movement of the jam element laterally toward the cable to thereby jam the cable between the passage walls and the jam element so as to prevent further movement thereof in that direction.
U.S. Pat. No. 4,674,778 discloses a locking ring formed of a plurality of curved clamp portions connecting in an end-to-end relationship for securing an electrical power measuring device with a mounting base. The semi-circular clamp portions are molded from a single piece of plastic, are identical in construction and are fully interchangeable. Each clamp is preferably formed with a semi-circular curved arc body having a male connection at one end and a female connection at the other end. The male end is formed with a pair of projections of which the first male projection serves as an alignment guide during make-up and use while the second male projection carries a movable latch shoulder for effecting the end-to-end connection with the adjacent mating clamp portion. The female end includes a housing having a central opening with separated first and second entrances formed by a roof mounted lug. The lug also forms a locking surface for engaging with the latch surface of the second male projection of the adjacent clamp portion to operably connect the clamp portions. A tampering indicating locking block is forced into the second entrance after the clamp portions are connected to block movement of the second male projection that would disengage the latch shoulder.
U.S. Pat. No. 4,883,295 discloses a tamper deterrent assembly which is molded of plastic material and includes a body member with an enclosed locking space having an open end. The open end is closed by a closure member mounted on the body member and movable toward a closed end of the locking space. The closure member is normally retained on the body member in a first position and may be moved to a locking position where a strip engaging unit carried by the closure member is received and locking by a locking unit. The locking unit may be carried by an elongated locking strip which is inserted into the locking chamber through a strip receiving slot in the body, or the strip engaging unit may pass through the locking strip and engage a locking unit carried on an end wall of the body.
What is needed in the industry is a simpler locking device to serve the desired purpose and this invention fills that need.